In one well-known frozen section procedure, a cold chuck is retrieved from a cryostat (at approximately −20 degrees Celsius). A small amount of a viscous embedding material, which is also known as a tissue freezing compound, is placed on the generally planar surface of the chuck, which may be textured, and the tissue sample is then placed into the embedding material. The embedding material may be OCT (Optimum Cutting Temperature); e.g. Tissue-Tek™ provided by Sakura Finetek. The combination of OCT and the tissue sample is referred to herein as a tissue specimen. It is generally understood that the tissue specimen is supported on a platform (such as a chuck) and/or contained in a receptacle (such as a mold). The chuck and tissue specimen are then placed back into the cryostat chamber and cooled until the tissue specimen is frozen. During this freezing process, a heat sink, also known as a weighted heat extractor, may be placed onto the tissue specimen to flatten the tissue sample and accelerate the freezing process. The frozen tissue sample is then sectioned using a microtome/cryostat. A section is typically several micrometers thick. The sections are then processed by methods that are well known to those skilled in the art. A medical practitioner then evaluates the processed sections.
The ability to produce full face microscopic sections of the true deep margin of the excised tissue relies on three important steps in the frozen section process. First of all, the tissue must be laid down so that the deep margin of the tissue lies in the same plane. Secondly, this planar orientation must be maintained during freezing. Finally, the frozen tissue sample needs to be oriented parallel to the sectioning plane of the microtome. A breach of any of these steps can result in excessive microtome “trimming in” before a full face section is obtained, potentially exposing a portion of a tumor which did not extend to the true deep margin.